Bartók spent many of his adult years traveling around modern-day Hungary and Romania collecting folk music.

[1] One of the first few known examples of Bartók pursuing artistic ambitions and reharmonizing songs without doubling the main melody was Eight Hungarian Folksongs.

[2] Since Bartók started using in the 10s and 20s much of the folk material he collected in the early 20th century, he also recomposed some of the sets, with newer harmony and no voice doubling.

[4] Kálmán Nádasdy, Medgyaszay's teacher, confirmed that Bartók used those sketches during rehearsals and even managed to make copies of songs 1, 2, 4, and 8 of the original set.

Since the revised set was not intended to be published or performed again, the pieces had to be thoroughly reconstructed from the sketches, as only the piano part was available and song No.